Optimised preparation and characterisation of electrospun (WO3) nanofibers for vapour sensing
摘要
Metal oxide semiconductor (MOS) materials are widely recognised for their excellent gas sensing properties due to their high sensitivity, potential for miniaturisation, and durability. In this work, tungsten trioxide (WO3) nanofibres were synthesised utilising an electrospinning technique on glass substrates, employing ammonium metatungstate hydrate and polyvinyl alcohol (PVA) as precursors. The electrospun films were vacuum annealed at 50 °C for 35 min, followed by calcination at 400 °C for 12 h to achieve highly crystalline nanograins. The properties of the material were investigated utilising Fourier-transform infrared spectroscopy, Hall effect measurements, Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM indicated a porous nanofibrous network with interconnected grains, contributing to a high surface area and facilitating gas adsorption. XRD analysis indicates the hexagonal crystal structure and polycrystalline nature of the prepared film, while BET analysis confirms that the average pore size of the WO3 samples depend on synthesis duration. The samples synthesised for 4 h, 5 h, and 6 h exhibit average pore sizes of 10 nm, 20 nm, and 40 nm, respectively, indicating that synthesis time significantly influences pore structure evolution. Additionally, XPS analysis confirms the main oxidation state of tungsten in WO3. The W⁶⁺ state in stoichiometric WO3 is compatible with the two distinctive peaks in the high-resolution W4f spectrum at binding energies corresponding to W4f5/2 and W4f7/2. Gas sensing properties of WO3 nanofibres were evaluated by exposure to 20 ppm of various volatile organic compounds (VOCs) across a temperature range of up to 400 °C. The sensor exhibited optimal performance at 350 °C, indicating high sensitivity towards ammonia vapour. At 10 ppm of ammonia, the sensor achieved a rapid response and recovery time of 22 s and 21 s, respectively. The enhanced sensing performance is attributed to the high surface area and porous nanostructure observed in SEM, which promotes effective gas diffusion and surface interaction. These findings demonstrate the potential of electrospun WO3 nanofibres for efficient ammonia detection in environmental monitoring applications.